Romelu Lukaku scored twice for ​Manchester United as they saw off Huddersfield 2-0 in their FA Cup fifth round tie, though the game will be remembered for a controversial decision made using the ​much maligned VAR system.

Juan Mata's effort on the stroke of half-time was eventually ruled out for offside after VAR deliberation, with official Neil Swarbrick determining the Spanish midfield maestro was marginally offside. Controversy arose however, after graphics displayed on screen suggested that the evidence used by Swarbrick to make his decision was less than conclusive.

In another bitter blow for the game's governing body, subsequent replays showed the former ​Chelsea man was perhaps level.

As it is, the decision not to award the goal had no bearing on the result of the game, as Lukaku's brace sealed the ​Red Devils passage into the quarter-finals, despite a spirited performance from David Wagner's side.

The ​Terriers made four changes from last weekend's win against ​Bournemouth, with midfield ace Aaron Mooy missing out through injury, while Jose Mourinho made six changes from the team beaten at St James' Park on Sunday. Michael Carrick returning to skipper the side, as Mourinho opted to lead his attacking line with star duo Alexis Sanchez and Romelu Lukaku.

The game got off to a pulsating start, with United stunning the home crowd with a goal in just the third minute. Played through by Mata's precise through ball, Belgian striker Lukaku showed tremendous composure and strength to hold off Christopher Schindler, before slotting past Jonas Lossl in the home goal.

Despite the early setback, the home fans were in fine voice, as the magic of the FA Cup produced a cracking atmosphere at the John Smith's Stadium. The home side almost gave them something to cheer about in response, as Tom Ince found space before narrowly firing wide of the far post.

Mourinho's men were finding themselves pinned in their own half during the opening 20 minutes, as Wagner's side boxed them in with an intense high press. Florent Hadergjonaj and Rajiv van La Parra both had shots saved by Sergio Romero, before Ince came close once more with a flashing effort at goal.

The visitors had failed to muster much attacking threat, before Mata neatly rounded Lossl, before converting Ashley Young's right wing pass. Immediately referee Kevin Friend referred to his ear piece to check the marginal offside decision, though the subsequent farce that followed will have done little to convince fans that the technology is ready to be used at the highest level of English football.

Disappointment aside, the visitors came out in the second half with more intent, and penetrated the ​Huddersfield back-line ten minutes into the second half. Hitting their opponents on the counter attack, Alexis Sanchez split the high-lined defence with a perfectly weighted pass, that Lukaku strode on to collect.

Much like he did in the first half, he took his time, shifting the ball onto his favoured left-foot before firing past Lossl at the near post for his 21st goal of the season.

The goal seemed to take the wind out of Huddersfield's sails, as the relegation threatened side began to run out of puff. Philip Billing forced another comfortable save for Romero, but in truth, Mourinho's defence had done more than enough to wear out and stifle their opposition with some dogged defending.

It wasn't a classic performance from Mourinho's side mind you, with their two goals providing the only shots on target that United had throughout the match. They did enough though, and now can look forward to an eighth FA Cup Quarter-Final tie in 11 years.